Waste Plastics injection in a Blast Furnace Nov14

Waste Plastics injection in a Blast Furnace...

Waste Plastics injection in a Blast Furnace The recycling of waste plastics (WP) by injecting them in a blast furnace (BF) is being practiced in few BFs especially in japan and Europe. The use of plastics in the BF also recovers energy from the WP and so it is sometimes considered as energy recovery. BF based ironmaking processes can utilize WP by any of the following methods. Carbonization with coal to produce coke. Top charging into the BF, although this generates unwanted tar from the decomposition of the plastics in the shaft. Gasifying the plastics outside the BF. The resultant synthesis gas is then injected through the tuyeres. Injection as a solid through the tuyeres in a similar way to pulverized coal (PC). Normally it is done as a co-injection of WP and coal into the BF. The first attempt for the waste plastics injection (WPI) in a BF was made at the Bremen Steel Works in 1994, with commercial injection starting a year later. The first integrated system for injecting plastic wastes was at NKK’s (now JFE Steel) Keihin Works in Japan. Injecting WP into BF has several environmental, operational and economic advantages. These include the following. Reduction in the amount of plastic wastes being landfilled or incinerated. Lower consumption of both coke and PC, thus saving coal resources. However, neither WP nor PC can completely replace coke. The amount of coke replaced in the BF is partly dependent on the quality of the WP. There is energy resource savings. The benefit of saved resources from mixed WPI is around 11 giga calories per ton (Gcal/t). There is decrease in the carbon dioxide (CO2) emissions since the combustion energy of WP is generally at least as high as that of PC normally injected,...

Cleaning of Blast Furnace Gas Jan22

Cleaning of Blast Furnace Gas...

Cleaning of Blast Furnace Gas The process of liquid iron production in the blast furnace (BF) generates gas at the furnace top which is an important by-product of the BF process. This top gas of the blast furnace is at the temperature and pressure existing at the BF top and usually contaminated with dust and water particles. This top gas is having substantial calorific value and is known as raw BF gas or contaminated BF gas. The composition and quantity of this top gas depend on the nature of the technological process in the blast furnace and the type and the quality of the raw materials used for the iron production in the blast furnace. In order to further use the raw BF gas, it is necessary to clean it by using certain process systems which reduces its content of the solid particles. The top gas contains carbon mono oxide (CO) and is known as blast furnace gas after its cleaning. It is used as fuel gas for heating blast air in the hot blast stoves as well as supplemental fuel in the steel plant. For the BF gas to be used as fuel gas, it is necessary that the raw BF gas is cleaned and cooled to reduce gas volumes and moisture content. Prior cooling and reduction in gas volume is also necessary since it results in substantial savings in delivery costs throughout the extensive distribution system of the steel plant. Typical analysis of the blast furnace gas for a blast furnace operating with pulverized coal injection (PCI) is given in Tab 1. The process systems for the gas cleaning are either wet gas cleaning system or dry cleaning system. High-efficiency gas cleaning systems are vital for the reliable operation and long campaign...

Factors affecting Coke rate in a Blast Furnace Jun29

Factors affecting Coke rate in a Blast Furnace...

Factors affecting Coke rate in a Blast Furnace  BF is a counter current reactor in which the reducing gas is produced by the gasification of the carbon of the BF coke with the oxygen of the hot blast injected via tuyeres in the lower part of the furnace. The reducing gas flows upwards reducing the iron bearing burden materials charged at the top of the furnace. Coke rate is the parameter for the consumption of BF coke which is measured in kilograms of BF coke consumed per ton of hot metal produced. Blast furnace (BF) coke is a key material for BF ironmaking, acting as a major energy source (fuel), a reductant, a carburization agent and a permeable structural support. There is no other satisfactory material available, which can replace, fully or partially, BF coke as a permeable support of blast furnace charge. BF coke is the most important raw material fed into the blast furnace in terms of its effect on blast furnace operation and hot metal quality. A high quality BF coke is able to support a smooth descent of the blast furnace burden with as little degradation as possible while providing the lowest amount of impurities, highest thermal energy, highest metal reduction, and optimum permeability for the flow of gaseous and molten products. Introduction of high quality BF coke to a blast furnace results in lower coke rate, higher productivity and lower hot metal cost. Role of coke in improving the BF performance is shown at Fig 1. Fig 1 Role of coke in improving BF performance A realistic assessment of the likely performance of coke in the blast furnace operating with or without injection technology includes those properties of coke that reflect its resistance to degradation under the chemical and...

Blast Furnace Gas Top Pressure Recovery Turbine Jun24

Blast Furnace Gas Top Pressure Recovery Turbine...

Blast Furnace Gas Top Pressure Recovery Turbine  Modern blast furnaces in steel plants operate at a high top gas pressure. The blast furnace (BF) gas leaving the BF at the top still maintain a pressure of around 1.6 kg/sq cm (g) to 3 kg/sq cm (g) and has a temperature of around 200 deg C.  This BF gas which is coming out at the top of a BF is cleaned to remove dust and the cleaned gas is used in the steel plant as a fuel for heating purpose at a relatively low pressure. In the process, a large amount of pressure energy is lost across the valve. BF gas top pressure recovery turbine (TRT) is a mechanism that utilizes the BF gas heat and pressure energy to drive a turbine.  The work generated by the turbine is transferred to a generator and converted to electric power. TRT generates power by exploiting a known property of all gases which is the expansion of gas volume with the reduction of its pressure. The system comprises dust collecting equipment, a gas turbine, and a generator. TRT is basically an energy saving measure at the BF which utilizes the waste pressure energy of the BF top gas to generate electric power. A TRT unit can produce around 15 to 60 kWh/t of hot metal (HM). Its output can meet around 30 % of the power needed by the all equipment (including the air blower) of the BF. The BF gas leaving the TRT unit can still be used as fuel in the steel plant. During iron making process, BF gas with high pressure and temperature is produced in blast furnace. In conventional practice, the energy of BF gas is wastage by pressure reduction at septum valve. Equipping TRT...

Fuel gases used in steel industry...

Fuel gases used in steel industry Fuel gas is a fuel which under ordinary conditions is in the form of gas. Fuel gases are used in steel plants for different applications which include (i) a source of heat (ii) as a reductant and (iii) cutting and welding application. Fuel gases usually used in steel industry are natural gas (NG), liquefied petroleum gas (LPG), acetylene, by product gases (blast furnace gas, coke oven gas and converter gas). Natural gas Natural gas is a gaseous fossil fuel which is extracted from deposits in the earth. It is a mixture of hydro carbons consisting primarily of methane (generally greater than 80 %) but includes varying amounts of other higher alkanes such as ethane, propane and butane etc. It may even contain some small percentage of nitrogen, carbon dioxide and hydrogen sulphide. It is an odorless, colourless, tasteless and non toxic gas. Natural gas is lighter than air and it burns with a clean blue flame when mixed with the requisite amount of air and ignited. It is considered one of the cleanest burning fuels. On burning it produces primarily heat, carbon dioxide and water. Quantities of natural gas are measured in normal cubic meters (corresponding to 0 deg C and I Kg/Sq cm pressure) or standard cubic feet (corresponding to 16 deg C and 14.73 psia pressures). The higher heat value of one cubic meter of natural gas varies from around 9500 Kcal to 10,000 Kcal. Its density is around 0.85 Kg/Cum. The main usage of natural gas in the steel industry is in iron making. For production of direct reduced iron it is reformed to produce reducing gases which are then used for the reduction of iron ore. The main reforming reactions are as follows. 2CH4...